Credit Losses - Customer Advance for Regulatory Capital and Notes Receivable (Details) - USD ($) $ in Thousands		Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 18, 2019
Short-term Debt [Line Items]
Customer advance for regulatory capital requirements, net of allowances	[1]	$ 39,955	$ 40,000
Customer advances, allowances		45
Long-term debt, net of discount		296,676	293,667
Notes receivable, net		$ 1,400
Premium ratio to Surplus		10
Prepaid expenses and other assets
Short-term Debt [Line Items]
Notes receivable, allowances		$ 14
Other noncurrent liabilities
Short-term Debt [Line Items]
Notes receivable, allowances		37
Equity Method Investee | Line of Credit
Short-term Debt [Line Items]
Face amount				$ 5,000
Interest rate				6.50%
Long-term debt, net of discount		$ 1,400	$ 1,000
Loss given default rate assumed		50.00%
Passport Note | Loans Payable
Short-term Debt [Line Items]
Interest rate					6.50%
Minimum risk-based capital requirement					150.00%

[1] See Note 18 for amounts attributable to related parties included in these line items.